Kathy, this is my 2 cents, which very often is not worth an awful lot. But here goes. Being in the nursery business for so many years (and of course my own gardens), I have seen alot of weird stuff happen with weather and tender plants.
I would grow en masse a plant named impatiens, to be a little more specific the "super elfin" series. My customers would rave about these plants of beauty and I would take orders for many of them (that I knew I could trust to come through the following season). I probably would have planted maybe 200 flats. I am sure that you would know what a flat is, but in case, it is 12 small containers in a tray with 4 plants in each container. 48 plants totalled.
Impatiens are extremely tender plants, they love heat and humidity. I would open for business about the 3rd week in April, and when my customers chose to purchase the impatiens before the first week of May, I would warn them to not plant them out until after this first week of May. There is still a chance that we may have a frost one night. Well. People get exhuberant in spring and many people had bought impatiens. Many people had set them outside. Of course they came back crying the blues that their impatiens had died.
Now I know from my own experience with tender annuals about frost. I would explain to my clients that even though the plants looked terrible and appeared dead, because the frost was not deep and did not touch the roots, the plants would be OK. Just to please be patient. Of course they all thought that I was from outer space. But I told them to trust me. This they did, they put their impatiens' lives trust in me and did not rip them out of the ground in disgust. ALWAYS, I would have these once sad customers come back and tell me that the impatiens had come back, they had grown new leaves and they look absoutely awesome. I would always smile inside because I knew that they would. The same thing had occurred when clients set their impatiens out in direct sunshine, leaf burn (they were grown in a greenhouse with fibreglass panels, so only filtered light). I would explain to them that the impatiens love to grow in the direct sunshine, but because because they had been grown under filtered light all their lives, they would need to adjust to the burning sunrays. Most of my clients liked to have impatiens for their dappled or shady spots, so most of them did not encounter the leaf burn. But I will tell you, I seen this many times with my own, after that initial sunburn, the plants were shorter, far more flowers and certainly much, much stronger than ones that were grown in the dappled sun or shade.
Eeeks!!! I carry on now don't I sometimes. I only had a short comment to make to you, but it turned into a novel!!!! (LOL).
The roots of your tomato plants were not affected by the frost. (Had the roots been frozen, the plant would surely have perished). That is why the plants still grew and you had the best tomatoes. That is natures way of thanking you for not ripping these poor little plants out of the ground, when you thought that they had gone by the wayside.
Anyways, there ya go, a short lesson on frost burn on leaves of plants.
I can't say for sure that this goes for ALL plants, just my experiences with some of the more tender ones. There are many others that I have experienced this sun and frost burn with too. Have the sweetest day. Cindi